Media Galleries API: Fix MediaGalleriesPreferences finders race.

chrome/browser/media_galleries/media_file_system_registry.cc

Index: chrome/browser/media_galleries/media_file_system_registry.cc
diff --git a/chrome/browser/media_galleries/media_file_system_registry.cc b/chrome/browser/media_galleries/media_file_system_registry.cc
index 25004bdcccc58c920f4d2d0643edb4d6a1b2edb9..d446fa538f302ad3eca2add397227b3fce5c573e 100644
--- a/chrome/browser/media_galleries/media_file_system_registry.cc
+++ b/chrome/browser/media_galleries/media_file_system_registry.cc
@@ -438,64 +438,21 @@ void MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
   Profile* profile =
       Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());
   MediaGalleriesPreferences* preferences = GetPreferences(profile);
-  MediaGalleryPrefIdSet galleries =
-      preferences->GalleriesForExtension(*extension);
-
-  if (galleries.empty()) {
-    callback.Run(std::vector<MediaFileSystemInfo>());
-    return;
-  }
-
-  ExtensionGalleriesHostMap::iterator extension_hosts =
-      extension_hosts_map_.find(profile);
-  if (extension_hosts->second.empty())
-    preferences->AddGalleryChangeObserver(this);
-
-  ExtensionGalleriesHost* extension_host =
-      extension_hosts->second[extension->id()].get();
-  if (!extension_host) {
-    extension_host = new ExtensionGalleriesHost(
-        file_system_context_.get(),
-        base::Bind(&MediaFileSystemRegistry::OnExtensionGalleriesHostEmpty,
-                   base::Unretained(this), profile, extension->id()));
-    extension_hosts_map_[profile][extension->id()] = extension_host;
-  }
-  extension_host->ReferenceFromRVH(rvh);
-
-  extension_host->GetMediaFileSystems(galleries, preferences->known_galleries(),
-                                      callback);
+  preferences->EnsureInitialized(base::Bind(
+      &MediaFileSystemRegistry::FinishGetMediaFileSystemsForExtension,
+      weak_factory_.GetWeakPtr(),
+      rvh,
+      extension,
+      callback));
 }
 
 MediaGalleriesPreferences* MediaFileSystemRegistry::GetPreferences(
     Profile* profile) {
-  MediaGalleriesPreferences* preferences =
-      MediaGalleriesPreferencesFactory::GetForProfile(profile);
-  if (ContainsKey(extension_hosts_map_, profile))
-    return preferences;
-
-  // Create an empty entry so the initialization code below only gets called
-  // once per profile.
-  extension_hosts_map_[profile] = ExtensionHostMap();
-
-  // TODO(gbillock): Move this stanza to MediaGalleriesPreferences init code.
-  StorageMonitor* monitor = StorageMonitor::GetInstance();
-  DCHECK(monitor->IsInitialized());
-  std::vector<StorageInfo> existing_devices =
-      monitor->GetAllAvailableStorages();
-  for (size_t i = 0; i < existing_devices.size(); i++) {
-    if (!(StorageInfo::IsMediaDevice(existing_devices[i].device_id()) &&
-          StorageInfo::IsRemovableDevice(existing_devices[i].device_id())))
-      continue;
-    preferences->AddGallery(existing_devices[i].device_id(),
-                            base::FilePath(),
-                            false,
-                            existing_devices[i].storage_label(),
-                            existing_devices[i].vendor_name(),
-                            existing_devices[i].model_name(),
-                            existing_devices[i].total_size_in_bytes(),
-                            base::Time::Now());
-  }
-  return preferences;
+  // Create an empty ExtensionHostMap for this profile on first initialization.
+  if (!ContainsKey(extension_hosts_map_, profile))
+    extension_hosts_map_[profile] = ExtensionHostMap();
+
+  return MediaGalleriesPreferencesFactory::GetForProfile(profile);
 }
 
 void MediaFileSystemRegistry::OnRemovableStorageDetached(
@@ -514,6 +471,10 @@ void MediaFileSystemRegistry::OnRemovableStorageDetached(
        profile_it != extension_hosts_map_.end();
        ++profile_it) {
     MediaGalleriesPreferences* preferences = GetPreferences(profile_it->first);
+    // If |preferences| is not yet initialized, it won't contain any galleries.
+    if (!preferences->IsInitialized())
+      continue;
+
     InvalidatedGalleriesInfo invalid_galleries_in_profile;
     invalid_galleries_in_profile.pref_ids =
         preferences->LookUpGalleriesByDeviceId(info.device_id());
@@ -619,8 +580,10 @@ class MediaFileSystemRegistry::MediaFileSystemContextImpl
   DISALLOW_COPY_AND_ASSIGN(MediaFileSystemContextImpl);
 };
 
+// Constructor in 'private' section because depends on private class definition.
 MediaFileSystemRegistry::MediaFileSystemRegistry()
-    : file_system_context_(new MediaFileSystemContextImpl(this)) {
+    : weak_factory_(this),
+      file_system_context_(new MediaFileSystemContextImpl(this)) {
   StorageMonitor::GetInstance()->AddObserver(this);
 }
 
@@ -633,6 +596,44 @@ MediaFileSystemRegistry::~MediaFileSystemRegistry() {
   DCHECK(mtp_device_delegate_map_.empty());
 }
 
+void MediaFileSystemRegistry::FinishGetMediaFileSystemsForExtension(
+    const content::RenderViewHost* rvh,
+    const extensions::Extension* extension,
+    const MediaFileSystemsCallback& callback) {
+  Profile* profile =
+      Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());
+  MediaGalleriesPreferences* preferences = GetPreferences(profile);
+  DCHECK(preferences->IsInitialized());
+  MediaGalleryPrefIdSet galleries =
+      preferences->GalleriesForExtension(*extension);
+
+  if (galleries.empty()) {
+    callback.Run(std::vector<MediaFileSystemInfo>());
+    return;
+  }
+
+  ExtensionGalleriesHostMap::iterator extension_hosts =
+      extension_hosts_map_.find(profile);
+  if (extension_hosts->second.empty())
+    preferences->AddGalleryChangeObserver(this);
+
+  ExtensionGalleriesHost* extension_host =
+      extension_hosts->second[extension->id()].get();
+  if (!extension_host) {
+    extension_host = new ExtensionGalleriesHost(
+        file_system_context_.get(),
+        base::Bind(&MediaFileSystemRegistry::OnExtensionGalleriesHostEmpty,
+                   base::Unretained(this),
+                   profile,
+                   extension->id()));
+    extension_hosts_map_[profile][extension->id()] = extension_host;
+  }
+  extension_host->ReferenceFromRVH(rvh);
+
+  extension_host->GetMediaFileSystems(
+      galleries, preferences->known_galleries(), callback);
+}
+
 void MediaFileSystemRegistry::OnPermissionRemoved(
     MediaGalleriesPreferences* prefs,
     const std::string& extension_id,
@@ -733,6 +734,7 @@ void MediaFileSystemRegistry::OnExtensionGalleriesHostEmpty(
     // |extension_hosts| entry alone, since it indicates the profile has been
     // previously used.
     MediaGalleriesPreferences* preferences = GetPreferences(profile);
+    DCHECK(preferences->IsInitialized());
     preferences->RemoveGalleryChangeObserver(this);
   }
 }